An array antenna (e.g., a phased array antenna) comprises a plurality of antenna elements arranged on a grid, or similar layout. The antenna elements can transmit and/or receive respective signals to form a coherent signal having a particular radiation pattern. The coherent signal can be steered in a particular direction by delaying transmission and/or reception of at least one antenna element relative to another antenna element.
Owing to proximity between antenna elements in an array, mutual coupling between antenna elements can occur, which (if unaccounted for) can deleteriously affect operation of the array antenna.
Conventionally, to measure the mutual coupling between various antenna elements in an array, measurements can be taken between each and every pair of antenna elements. For example, a first channel of instrumentation (e.g., a network analyzer) can be connected to a first port of the array antenna connected to a first antenna element, and a second channel of the instrumentation can be connected to a different port connected to a second antenna element. A signal can be transmitted by the first antenna element, whereby a measurement can be taken (e.g., by the network analyzer) at the second antenna element to determine a mutual coupling occurring between the first antenna element and the second antenna element. The process can be repeated until the mutual coupling between all of the antenna element pairings is determined. With an array comprising a small number of antenna elements, such a conventional operation can be easily performed. However, in an array comprising a large number of antenna elements, e.g., 1,000 antenna elements, the task would soon become time consuming, as well as tedious. A multi-channel network analyzer (e.g., comprising 16 ports or channels) can be utilized to speed up the process by connecting a number of antenna elements concurrently. However, as more channels are incorporated into a multi-channel network analyzer there is a corresponding increase in cost, such that the cost of such a network analyzer may become prohibitive.